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[Libcdio-devel] Re: Submission of new mmc function for libcdio

From: Thomas Schmitt
Subject: [Libcdio-devel] Re: Submission of new mmc function for libcdio
Date: Fri, 29 Jan 2010 08:24:33 +0100


> There should be an additional parameter
> which is basically a driver_return_code_t that indicates whether the answer
> is valid or not, and if not gives some idea of what went wrong.

Good idea.

> The caller
> of this can also query SCSI sense data if this "valid" parameter says
> something went wrong.

There is a little problem with obtaining sense
reply in higher function levels:

The caller of mmc_get_disc_erasable() would have
to make the assumption that the function
performed only a single MMC command resp. that
the failed command was the last command
performed in that function.

This would hamper to implement complex MMC
gestures inside mmc_get_disc_erasable(). 

So if the sense reply is of meaning for
callers of callers of mmc_run_cmd(), then the
immediate caller of mmc_run_cmd() has to take
care of the sense reply.

Further: the sense is really meaningful only if
one knows from what MMC command it stems.

So i advise to convert the sense reply into a
libcdio error reply already inside the function
that directly calls mmc_run_cmd().

I admit mmc_get_disc_erasable() is not much of
a candidate for complexity. But in the general
case one should try to achieve good encapsulation
of the function entrails.

Have a nice day :)


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